The present application relates to a battery using a carbon material as a negative electrode active material.
In recent years, downsizing and weight saving of portable electronic devices represented by a mobile phone, PDA (personal digital assistant) and a laptop personal computer have been actively promoted. As a part thereof, an enhancement in energy density of a battery as a driving power source for such electronic devices, in particular, a secondary battery has been eagerly desired.
As a secondary battery capable of obtaining a high energy density, there are known, for example, secondary batteries using lithium (Li) as an electrode reactant. Above all, a lithium ion secondary battery using a carbon material capable of intercalating lithium in a negative electrode and deintercalating it therefrom is widely put into practical use.
However, in the lithium ion secondary battery using a carbon material for a negative electrode, technologies have already been developed to an extent close to a theoretical capacity thereof. Thus, as a method for further enhancing the energy density, there has been studied a method in which the thickness of an active material layer is increased, thereby increasing a proportion of the active material layer within the battery and decreasing a proportion of each of a collector and a separator (see, for example, JP-A-9-204936).